In 38 cases of Stage I lung cancer, for which surgery was not indicated because of poor cardiopulmonary function or other reason, radical irradiation yielded excellent results. The five year survival rate was 42.1%, the 10-year survival rate 28.4% and the 15-year survival rate 17.1%. Postradiation conlications which can be life-threatening, were acceptably low in incidence, and there was no radiation-related death. The results support the concept of radical irradiation being acceptable as a treatment modality for Stage I lung cancer if the patients concerned cannot have surgery because of poor cardiopulmonary function or some other reason.